The present invention relates in general terms to headlights of the elliptical type for motor vehicles.
Generally, a headlight of this type includes a reflector having a zone with a first focus, in the vicinity of which a light source is located, together with a zone with a second focus in the vicinity of which the radiation from the source is concentrated after being reflected by the reflector. A lens, which is typically a planar-convex spherical lens, is focused in the vicinity of the second focal zone, and projects the said concentrated radiation on the road.
It is also conventional to provide, in the second focal zone, a screen which is designed to occult part of the radiation and which has an upper edge that defines, in the beam which is formed, a cut-off line whereby to obtain a cut-off beam, and in particular a dipped beam.
Although these known headlights conventionally had a reflector in the form of an ellipsoid of revolution, with first and second point foci, the Applicant has recently proposed modification of such a reflector in order to generate, in the focal plane of the lens, a concentrated patch of light which is pre-widened, so as to give the required width to the projected beam.
In this way, recourse to optical elements (such as striations, prisms etc.), for spreading the light sideways, is limited by a substantial amount, such elements being always tricky to apply in a headlight of the type for projecting a light image of the kind produced by a headlight of the elliptical type.
The document FR-A-2 704 044 describes such a modified reflector.
However, the reflector described in that document does have certain other limitations. In particular, the very nature of the reflector leads to a beam for which a photometric study shows that it is capable of being improved.
It is useful to recall here that a satisfactory dipped beam, that is to say one having the maximum amount of visual comfort for the driver while conforming with the regulations in force, must include a patch of light having a relatively pointed concentration, either along the axis of travel, or slightly offset laterally towards the nearside (that is to say towards the right for driving on the right), and must also have a relatively homogeneous light over a certain width on either side of the patch of light concentration, with a relatively regular transition between the concentration and the spread light.
Now, the reflector of the above type leads in general to a beam which has a concentration zone of excessive width, and as a result, an excessively feeble light intensity. A further limitation of this known headlight lies in the fact that the beam may be insufficiently thick, that is to say it may have a high concentration of light just under the cut-off line, but not enough to illuminate the road closer to the vehicle.
In addition, the beams generated by headlights of the above type are generally of relatively reduced thickness, and in all cases they are difficult to control, although it is above all desirable to have, at least in the case of a dipped beam, a beam that is of substantial width towards the nearside, and which at the same time does not give rise to too much light in the axis of the vehicle and too close to the latter.
The present invention aims to overcome these disadvantages in the state of the art, and to propose a headlight of the above mentioned type in which the beam obtained is improved.
Another object of the present invention is to give the designer more flexibility in obtaining various features of the beam, such as width and intensity of the patch of light concentration, and evolution of the intensity towards the side edges of the beam.
Finally, another object of the present invention is to propose a headlight in which the thickness of the beam generated can be controlled more easily and with greater flexibility during its design.
Accordingly, the invention proposes a motor vehicle headlight, of the type adapted to generate a light beam of given configuration and comprising a light source, a reflector of the elliptical type, having a first focus in the vicinity of which the light source is situated, and a lens located in front of the reflector, is characterised in that the reflector has at least two zones which are situated side by side and which are adapted to form, in a focal region of the lens, patches of light which are preformed in width, and in that the patches overlap each other in a horizontal direction.
Features, preferred but not limiting, of the headlight in accordance with the invention are as follows:
each zone of the reflector has a surface with a horizontal generatrix such that the rays which it reflects from the rays issued from the source lie in vertical planes which intersect an imaginary line at two points, of which the curvilinear abscissas evolve on the said line in accordance with a predetermined law;
the said imaginary lines of the different zones are continuous;
the said imaginary lines of the different zones are curves;
each curve is spaced away from the focal region of the lens, in a direction parallel to the axis of the reflector, by an amount which is greater the more the said curve is spaced laterally away from the said axis;
in each zone of the reflector, a vertical section of the said reflector situated in a vertical plane containing the ray reflected by the horizontal generatrix is adapted to concentrate the said rays reflected on the said associated point of the imaginary line, the said imaginary line being a line of secondary foci, and the said points being secondary foci;
in at least part of one of the zones, an upper region of a vertical section is adapted to concentrate the rays which it reflects on another point which is situated between the said associated secondary focus and the lens;
on either side of a transition line between two adjacent zones, the vertical sections of the said zones have lines of secondary foci which are not superimposed;
the said transition line is determined by the intersection of the surfaces of the said zones, and the said transition line is distinct from the respective lines of constant horizontal deviation of the said zones;
the reflector has two zones which are separated by a transition line extending horizontally, substantially in the middle of the reflector;
the reflector has three zones which are separated by two transition lines lying on either side of the axis of the reflector;
a central zone of the reflector is substantially narrower in the horizontal direction than two lateral zones;
the headlight further includes a mask situated in the focal region of the said lens, so as to generate a cut-off beam;
the said lines of secondary foci are situated in the axial direction between the mask and the lens.